Custom UI Gallery Button

Question

I have a custom UI ribbon and I'm trying to include the mso gallery ShapeFillColorPicker. However, when I add it to my ribbon, it only appears as a gallery and doesn't include the splitbutton feature that the normal PPT ribbon includes.

I want to be able to

1. click it and apply a color

OR

2. click it and open a menu.

Currently it only does #2.

Is there a way to change the custom UI so that it does both #1 and #2?

Currently my custom UI is as follows:

gallery idMso="ShapeFillColorPicker" label=" "  showLabel="false"